Unpackaged or bare semiconductor dice are used to construct multi chip modules and other electronic devices. Unpackaged dice must be tested and burned in during the manufacturing process to certify each die as a known good die. This has led to the development of temporary packages that hold a single bare die for testing and burn-in. The temporary packages provide the electrical interconnection between the bond pads on the die and external test circuitry. Exemplary temporary packages are disclosed in U.S. Pat. Nos. 5,302,891; 5,408,190 and 5,495,179 to Wood et al., which are incorporated herein by reference.
Typically, this type of temporary package includes an interconnect having contact members that make a temporary electrical connection with the bond pads on the die. The temporary package can also include a force applying mechanism that presses the die against the interconnect. For example, in the above cited patents the force applying mechanism can include a clamp mechanism that attaches to a package base, and a spring that presses the die against the interconnect.
Typically, the interconnect for the temporary package includes a substrate wherein the contact members are formed. One type of interconnect is formed of silicon and includes raised contact members formed as etched pillars having penetrating projections. The penetrating projections are adapted to penetrate into the bond pads on the die to form a temporary electrical connection for testing. A conductive layer overlies each raised contact member and is in contact with a conductor (e.g., metal traces) formed on the substrate. The conductors can be wire bonded, or otherwise electrically connected, to corresponding external contacts on the base of the temporary package. This type of interconnect is described in U.S. Pat. No. 5,483,741 to Akram et al., which is incorporated herein by reference.
Another type of interconnect includes a substrate and microbump contact members mounted on the substrate. The substrate in this case can be silicon, or a low CTE material such as ceramic or glass. The microbump contact members and conductors can be in the form of a flexible tape similar to two layer TAB tape. This type of interconnect is described in U.S. Pat. No. 5,487,999 to Farnworth, which is incorporated herein by reference.
Both of these types of interconnects can include electrical or structural defects which can cause the die test procedure to be affected or invalidated. For example, an insulating layer that insulates the conductors of the interconnect from the substrate can be defective and allow current to leak from one or more conductors into the substrate. The substrate can also include cracks that propagate through the insulating layer creating undesirable electrical paths in the assembled temporary package.
This type of defect can be present as a result of the fabrication process for the interconnect. Also, since the interconnects are designed to be reused many times, defects can arise as a result of continued usage of an interconnect and package. For example, the interconnects and packages are repeatedly stressed by the force applying mechanism which biases the die and interconnect together. In addition, the interconnects and packages are repeatedly subjected to thermal cycling in a burn-in oven.
In view of the foregoing, it would be desirable to have a method for checking the electrical and structural integrity of interconnects for temporary packages used to test bare semiconductor dice. Furthermore, it would be desirable for a temporary package to be constructed to allow testing of the interconnect component in the assembled package.
Accordingly, it is an object of the present invention to provide a method for testing an interconnect for a bare semiconductor die. It is another object of the present invention to provide a method for testing the interconnect that can be performed in an assembled temporary package. It is yet another object of the present invention to provide a temporary package for testing the bare die that is constructed to allow testing of die and the interconnect component. Other objects, advantages and capabilities of the present invention will become more apparent as the description proceeds.